WO2015004908A1

WO2015004908A1 - Plate molding method and preliminary molded shape setting method

Info

Publication number: WO2015004908A1
Application number: PCT/JP2014/003620
Authority: WO
Inventors: 欣哉中川; 靖廣岸上; 雄司山▲崎▼
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2013-07-09
Filing date: 2014-07-08
Publication date: 2015-01-15
Also published as: EP3020492A4; KR20160030975A; JP5867657B2; CN105451908B; MX2016000001A; EP3020492B1; KR101815403B1; CN107737829A; JPWO2015004908A1; CN105451908A; US20160160311A1; CN107737829B; EP3020492A1; US10730090B2

Abstract

Provided is a plate molding method that enables both yield improvement and molding property improvement. The molding method for a plate (1) involves applying plastic deformation to a plate (1) to mold a preliminary molded shape and then plastically deforming the preliminary molded shape to obtain a final shape. With respect to the cross section at a plurality of positions in the final shape, the preliminary molded shape is determined so that the ratio (L1/L0) of a cross section line length (L1) in the preliminary molded shape to a cross section line length (L0) in the final shape, such line lengths being at the same cross-section position, falls within a range of allowable values set beforehand.

Description

Forming method of plate material and setting method of preformed shape

The present invention relates to a technique for applying a plastic deformation such as overmolding to a plate material in multiple stages to obtain a final shape.

In the case where a plate material is made into a final shape by press molding, improvement in yield and improvement in formability are important issues.

Generally, in order to improve the yield, it is desirable to make the amount of material flowing into the mold as small as possible during molding so that the molding conditions are close to the stretch molding. However, when the inflow of the material is too small, the material in the mold becomes insufficient at the time of molding, so that the plate thickness becomes excessively thin and cracks occur. On the other hand, if the molding is performed mainly by drawing in order to avoid cracking, the yield is reduced. Various approaches have been taken in the past to deal with such problems.

Patent Document 1 discloses a method of reducing the surplus and improving the yield by creating a range in which the blank material is not restrained in the initial stage of press molding. Further, Patent Document 2 discloses a method for avoiding a molding defect by allowing a local area of a press mold to be driven as an individual movable punch, and drawing a blank into the mold in advance and then performing molding with the movable punch. It is disclosed.

JP 2007-118021 A JP 2007-326112 A

In the method of Patent Document 1, it is possible to reduce the surplus as compared with the conventional method, but the surplus is still necessary. Moreover, since the method of patent document 1 is drawing, there is a limit in a yield and an improvement allowance.

Further, in the method of Patent Document 2, although it is possible to avoid molding defects, the yield is reduced because of the drawing.

The present invention focuses on the above points, and an object of the present invention is to provide a method for forming a plate material and a method for setting a preformed shape, which can improve both yield and formability.

Generally, it is known that when press molding is performed, the moldability is improved when the press molding is performed in multiple stages divided into a plurality of molding processes. The reason is that the strain is not concentrated in one place and the whole plate material is more concentrated in the case of forming in stages in multiple forming processes compared to the case of forming to the final shape in one forming process. This is because the strain is easily dispersed. However, the mold shape at the pre-molding stage prior to the final stage of press working largely depends on the experience of engineers, and a method for determining the shape has not been established.

The inventors have conducted a research study to effectively perform preforming in order to simultaneously solve the demands for both yield improvement and formability improvement. The inventors have found that if a cross-sectional line length comparable to that of the final shape can be obtained at the pre-molding stage, the final shape can be obtained at the time of final molding with almost the same strain distribution as during pre-molding. did.

[First means]
In order to solve the above problems, a method for forming a plate material according to one aspect of the present invention is to form a plate material that is plastically deformed from the preformed shape to the final shape after plastic deformation is applied to the plate material. In the method, for a plurality of cross-sections in the final shape, the ratio of the cross-sectional line length in the preformed shape to the cross-sectional line length in the final shape at the same cross-sectional position falls within a predetermined allowable range. Thus, the pre-formed shape is determined.

The preforming shape setting method according to one aspect of the present invention includes the preforming shape when the plate material is plastically deformed from the preformed shape to the final shape after being plastically deformed to form the preformed shape. The ratio of the cross-sectional line length in the pre-shaped shape to the cross-sectional line length in the final shape at the same cross-sectional position for a plurality of cross-sections in the final shape is a preset allowable value. The pre-shaped shape is determined so as to be within the range.

Here, the positions of the cross-sections at a plurality of locations are set in, for example, a lattice shape or a radial shape.

[Second means]
In order to solve the above-described problem, the plate material molding method according to one aspect of the present invention is obtained by plastically deforming a plate material into a preformed shape, and then plastically deforming from the preformed shape to the final shape. An inner reference point is set in the final shape molding region, and a plurality of outer reference points are set on the outer peripheral contour line of the molding region, and a first inner point corresponding to the inner reference point with respect to the final shape. And a plurality of cross-sectional lines individually connecting the first outer points corresponding to the respective outer reference points, and determining each divided point obtained by dividing the set cross-sectional lines at a preset ratio, and adjacent to each other. The length of the endless annular line obtained by connecting the dividing points is a first line length, and in the preformed shape, each of the second inner point corresponding to the inner reference point and each outer reference point A plurality of cross-sectional lines connecting the second outer point are set ratios as described above. The ratio of the second line length to the first line length when the length of the endless annular line obtained by connecting adjacent division points at each divided point is the second line length. The pre-shaped shape is determined so that the value falls within a preset allowable value range.

The preforming shape setting method according to one aspect of the present invention includes the above-described pre-formation in the molding of a plate material that is plastically deformed from the preformed shape to the final shape after plastic deformation is performed on the plate material. A molding shape setting method, wherein an inner reference point is set in a molding region of the final shape, and a plurality of outer reference points are set on an outer peripheral contour line of the molding region, and the inner side is set with respect to the final shape. A plurality of cross-sectional lines that individually connect the first inner point corresponding to the reference point and the first outer points corresponding to the respective outer reference points are set, and the set cross-sectional lines are divided at a preset setting ratio. Each of the dividing points to be obtained, and the length of an endless annular line obtained by connecting adjacent dividing points as a first line length, and in the preformed shape, a second inner point corresponding to the inner reference point; Each second outer side corresponding to each outer reference point When the length of an endless annular line obtained by connecting adjacent division points at each division point obtained by dividing a plurality of cross-sectional lines connecting the two at the set ratio is the second line length, The preforming shape is determined such that the ratio of the second line length to the line length falls within a preset allowable value range.

According to one aspect of the present invention, it is possible to obtain a cross-sectional line length comparable to that of the final shape at the pre-molding stage, so that the final shape can be obtained at the time of final molding with substantially the same strain distribution as that during pre-molding. Thus, it is possible to provide a plate material forming method and a preformed shape setting method capable of improving both yield improvement and formability improvement.

The present invention is particularly effective in the case of stretch forming.

For example, by adopting press molding for molding and applying the present invention, it is possible to achieve high yield while facilitating molding by overhang molding when performing press molding.

When stretch forming using a punch and die, the material is not distorted due to frictional resistance at the bottom of the punch when it is molded to the final shape at once. Thinner and more likely to crack. On the other hand, by introducing strain into the bottom of the punch in the final shape in the pre-molding stage, it is possible to improve the formability in the final molding stage in a pseudo manner.

In addition, since it is desirable to put strain uniformly throughout, it is desirable to perform pre-molding by a molding method that tends to make strain uniform, such as hydraulic bulge processing, but it is also possible to perform pre-molding by normal press working It is.

FIG. 1 is a conceptual diagram illustrating a molding process according to an embodiment of the present invention. FIG. 2 is a diagram relating to the first embodiment, and is a diagram illustrating a method for determining a preformed shape. FIG. 3 is a diagram relating to the first embodiment, and is a plan view showing a first example of positions of a plurality of cross-sections for obtaining a cross-sectional alignment. FIG. 4 is a diagram relating to the first embodiment, and is a plan view showing a second example of positions of a plurality of cross-sections for obtaining a cross-sectional alignment. FIG. 5 is a diagram relating to the first embodiment, and is a diagram illustrating a final shape in the first embodiment. FIG. 6 is a diagram related to the first embodiment, and is a diagram showing a pre-formed shape in Example 1, where (a) is a shape example according to the conventional method, and (b) is a shape example according to the method of the present invention. is there. FIG. 7 is a diagram relating to the first embodiment, and is a diagram illustrating a final shape in Example 2. FIG. 8 is a diagram relating to the first embodiment, and is a diagram showing a preformed shape in Example 2. FIG. FIG. 9 is a diagram relating to the second embodiment and is a diagram for explaining a method for determining a preformed shape. FIG. 10 is a diagram relating to the second embodiment, and is a plan view illustrating an example of setting internal reference points and external reference points. FIG. 11 is a diagram relating to the second embodiment, and is a diagram illustrating the setting of an endless annular line (first endless annular line) in the final shape. FIG. 12 is a diagram relating to the second embodiment, and is a diagram illustrating a position that becomes an unexpected annular line (second endless annular line) in a preformed shape. FIG. 13 is a diagram related to the second embodiment and is a diagram illustrating a final shape of the example. FIG. 14 is a diagram relating to the second embodiment, and is a plan view showing an endless annular line (first endless annular line) in the final shape of the example. FIG. 15 is a diagram relating to the second embodiment, and is a plan view showing an endless annular line (second endless annular line) in the preformed shape of the example.

Next, an embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

[First embodiment]
FIG. 1 is a conceptual diagram illustrating a molding process in the present embodiment.

As shown in FIG. 1, the molding of this embodiment is performed by pre-forming a plate material 1 (blank) plastically deformed into a pre-formed shape, and the plate material 1 having a pre-formed shape in the pre-forming step as a final product. It consists of a two-stage molding process and a main molding process that plastically deforms into a shape. Note that the preforming process itself may be composed of a plurality of preforming processes.

The preforming step is performed, for example, by press molding using a preforming mold for molding into the preformed shape. The mold includes, for example, a punch and die set.

Similarly, the main molding step is also performed by press molding using a main mold for molding into the final shape. The mold includes, for example, a punch and die set.

The above press molding is, for example, stretch molding.

In the present embodiment, prior to the preforming step, there is a process of obtaining the shape of the preforming mold, that is, the preformed shape from the final shape. When the preforming shape is determined, a preforming mold is manufactured so as to obtain the preformed shape.

The method for determining the pre-formed shape is to set a plurality of cross-sections along the plate thickness direction of the plate material 1 in the final shape, and the cross-section in the pre-formed shape with respect to the cross-sectional line length in the final shape at the same cross-sectional position. The preforming shape is determined so that the ratios of the line lengths are within the allowable range set in advance. That is, the pre-formed shape is determined by comparing the cross-section line lengths of the final shape and the pre-formed shape so that the ratio of both cross-section line lengths falls within a preset allowable range. Determine the shape.

The direction “along the plate thickness direction of the plate 1” corresponds to the pressing direction.

2 shows a processing example of a method for determining a preformed shape based on the final shape.

That is, two or more cross-sectional locations are set for the plate material 1 (Process A). It is preferable that the cross-sectional location is set so as to pass through a characteristic location where the curvature of the cross-sectional shape in the final shape is at least steep. By doing so, it is possible to reduce the number of cross sections to be set.

FIG. 3 shows a first setting example of the positions of a plurality of cross sections.

That is, in the example shown in FIG. 3, the positions of the cross-sections at a plurality of locations are in an n × m lattice shape when viewed from the direction along the plate thickness direction of the plate material 1 before forming (corresponding to the projecting direction by plan view). This is an example when (n + m) cross-sectional portions are set in (mesh shape). The setting location will be described later. In addition, the outer periphery outline of a shaping | molding area | region is corresponded to the external shape line of a final shape.

Next, for the final shape, the cross-sectional line lengths at the plurality of locations set above are obtained (Process B). The cross-sectional line length L0 of the final shape is acquired by performing a molding simulation of the final shape using, for example, CAE (Computer Aided Engineering). Further, the cross-sectional line length L0 of the final shape may be obtained by actually performing press molding to produce a final-shaped product and measuring the cross-sectional line length L0 by an optical measurement method or the like. But the acquisition method of cross-sectional line length L0 is not limited to this, What is necessary is just to employ | adopt a well-known method.

Next, in the pre-formed shape, the cross-sectional line length L1 at the same position as the cross-sectional position set in the final shape is the cross-sectional line length corresponding to the acquired corresponding cross-sectional line length. The cross-sectional line length L1 is specified (processing C). At this time, the cross-sectional line length L1 at each cross-sectional location is set, for example, within the allowable range described later.

The section line length corresponding to the section line length is a section line length when the ratio of the section line length in the preformed shape to the section line length in the final shape is within a preset allowable range. In the present embodiment, the range of the preset allowable value is a range in which (L1 / L0) is 0.8 times or more and 1.2 times or less. Under this condition, the cross-sectional line length of the final shape and the cross-sectional line length of the preformed shape are set to be the same in the same cross section.

Next, the preformed shape is specified so as to satisfy all the conditions of the cross-sectional line length L1 of each specified cross-sectional location (Process D).

Here, in the processing A described above, the accuracy increases as the number of cross-sectional portions for obtaining the cross-sectional line length increases. Although how to take a cross-sectional location is free, it is preferable to employ at least two cross-sectional locations.

Here, orthogonal coordinates are considered with the plate thickness direction of the plate material 1 before forming as the Z-axis and the directions orthogonal to the Z-axis as the X-axis and the Y-axis. At this time, the X-axis and the Y-axis are directions along the surface of the plate material 1 before molding.

In the first setting example shown in FIG. 3, n locations and cross-sectional locations are set in parallel with the XZ plane at predetermined intervals, and m locations and cross-sectional locations are set in parallel with the YZ plane at predetermined intervals. n and m are 1 or more.

When the values of n and m are set to 2 or more, the cross-sectional portion is set in a lattice shape (mesh shape) as viewed from the plate thickness direction of the plate material 1 before forming. The lattice shape does not need to be an orthogonal lattice shape. The cut portions may be set in at least two directions intersecting each other in plan view, and a plurality of cross-sectional shapes may be used in each direction. Moreover, when the plate | board thickness direction of the board | plate material 1 before shaping | molding and a press direction are not parallel, it is preferable to set so that the surface direction of each cross section may not be parallel to a Z axis | shaft but parallel to a press direction.

In addition, as described above, it is preferable to select a cross section that passes through many places where the curvature in the final shape changes more steeply than previously set. Further, the line specifying the cross section may not be a straight line, but it is easier to set it to a straight line.

When determining the pre-formed shape at the cross-sectional location in the two directions, for example, after temporarily determining the shape of the pre-formed shape from the cross-sectional alignment from the direction in which the degree of curvature change is relatively small, the other direction The shape of the final preformed shape is determined by correcting with the cross-sectional alignment in FIG.

The ratio of the sectional line length between the final shape and the preformed shape is preferably in the range of 0.8 times to 1.2 times as described above, and is preferably in the range of 0.9 times to 1.1 times. Further preferred. It has been confirmed that the occurrence of cracks and the occurrence of wrinkles on the product surface can be significantly reduced by adjusting the range from 0.8 times to 1.2 times. Since it was confirmed that a high yield was secured at least within this range, this value was specified.

Here, the example shown in FIG. 3 is an example in which a plurality of cross sections are set in a lattice shape. The setting of the cross sections at a plurality of locations is not limited to this.

Next, FIG. 4 shows a second setting example for setting the positions of the cross sections at a plurality of locations.

This example is an example in which the positions of a plurality of cross sections are set radially. That is, as viewed from the direction along the pressing direction (the direction along the plate thickness direction of the plate material before forming), the internal set point P ₀ is set in the forming region of the final shape, and passes through the internal set point P _0. In addition, a plurality of lines CA ₁ to CA ₈ extending in different directions are set, and the plurality of cross sections are set at the positions of the set lines.

FIG. 4 illustrates the case where the plurality of lines are eight, but may be other than eight. However, the number of cross sections is preferably 8 or more. In addition, when the accuracy to be obtained is the same, the number of cross-sections can be reduced in the radial setting compared to the grid setting.

Also, the radially extending lines need not be set at regular intervals. It is preferable to set so as to pass through a portion having a large curvature change in the final shape.

FIG. 4 illustrates the case where both ends of the line passing through the internal set point P0 are a single line that reaches the outer peripheral contour line of the final shape forming region. However, FIG. As shown, each line may be set so as to connect the internal set point P0 and one point of the outer contour line of the final shape forming region. In this case, there are 16 lines in the example of FIG. The “molding region” indicates a region in which plastic deformation is positively applied including a product surface, a pre-formed portion, etc., in a press product after preforming or main molding. However, the part molded by the bead is not included.

Also, the internal set point P0 is preferably set at the position of the centroid when the molding area is viewed from the direction along the press direction.

Here, in the above description, the case where the final shape is formed by the two-stage forming process of the pre-forming process and the main forming process has been described as an example. The pre-molding process may be composed of two or more temporary molding processes.

In this case, the processed shape after processing in each of the temporary forming steps is a cross-section in the processed shape after the processing with respect to the cross-sectional line length in the final shape at the same cross-sectional position for a plurality of cross-sectional locations in the final shape. It is preferable to set the wire length for each of the temporary forming steps so that the wire lengths are within the allowable range. However, it is only necessary that the preformed shape one stage before forming into the final shape satisfies the above conditions.

Here, the present invention can be applied not only to automobile parts but also to all processes for press-molding the plate material 1. The material for press molding is not limited to steel, but can be applied to ferrous alloys such as stainless steel, non-ferrous materials, and non-metallic materials.

In particular, it can be applied to high-tensile materials that have been difficult to apply.

[Second Embodiment]
FIG. 1 (same as FIG. 1 used in the description of the first embodiment) is a conceptual diagram illustrating the molding process in the present embodiment.

The above press molding is, for example, stretch molding.

The preforming shape determination method sets an inner reference point in the molding region of the final shape and sets a plurality of outer reference points on the outer peripheral contour line of the molding region, A plurality of cross-sectional lines passing through the first inner point corresponding to the reference point and the first outer points corresponding to the respective outer reference points are set, and the set cross-sectional lines are divided at a preset setting ratio. Each division point is obtained, and the length of an endless annular line obtained by connecting adjacent division points is a first line length. In the preformed shape, the second inner point corresponding to the inner reference point and the above The length of an endless annular line obtained by connecting adjacent division points at each division point obtained by dividing a plurality of cross-sectional lines connecting each second outer point corresponding to each outer reference point by the set ratio is Above the first line length when the line length is 2. As within the range of tolerance ratio of the second line length is preset to determine the preformed shape. Here, a method for setting the outer point in the preformed shape will be described. The inner reference point set to the final shape is set as the origin, and the press direction is set as the Z direction. Then, three-dimensional coordinates are set with the directions indicated by two orthogonal straight lines passing through the origin and orthogonal to the Z direction as the X direction and the Y direction. Then, each outer reference point can be expressed using the X, Y, and Z coordinates. Next, the X, Y and Z coordinates are similarly set in the space for designing the preformed shape, and the outer reference in the design space for the preformed shape is referred to by referring to the coordinates of each outer reference point obtained by the above method. It becomes possible to obtain points.

That is, in the final shape, an endless annular line having a contour line (annular ring shape) centered on the first inner point is set and the first line length is obtained, and the endless line corresponding to the endless annular line in the preformed shape is obtained. The pre-shaped shape is determined so that the second line length of the annular line falls within a preset allowable value range with respect to the first line length. The endless annular line preferably employs a cross-sectional line in each shape.

FIG. 9 shows a processing example of a method for determining a preformed shape based on the final shape.

First, in step S10, as shown in FIG. 10, an inner reference point A is set in the forming region that is the final shape of the plate material 1 before forming, and a plurality of outer reference points B1 are formed on the outer peripheral contour line of the forming region. Set ~ B8.

The inner reference point A is, for example, when the final shape is viewed from the centroid of the molding region that is the final shape in the plate material 1 before molding or the direction along the press direction with respect to the plate material 1 after molding into the final shape. Set to the position of the centroid.

The plurality of outer reference points B1 to B8 are set along the outer peripheral contour of the molding region on the outer peripheral contour of the molding region. The plurality of outer reference points B1 to B8 need not be set at equal intervals.

Further, in this embodiment, the case where the positions of the plurality of outer reference points B1 to B8 are set on the plate material 1 before molding is illustrated, but the outer peripheral contour line (outer shape) of the molding region on the plate material 1 after final formation is illustrated. It is preferable that the positions of the plurality of outer reference points B1 to B8 are set by lines), and the positions corresponding to the positions are set in the plate material 1 before forming.

It is possible to set the outer reference points B1 to B8 at more appropriate positions by setting the positions of the plurality of outer reference points B1 to B8 on the outer peripheral contour line (outline) of the forming region in the plate 1 after the final formation. Become. That is, setting the outer reference points B1 to B8 so as to pass through a cross-sectional position where the curvature change is large (for example, a steep position) can improve the accuracy while reducing the number of outer reference points B1 to B8.

) The greater the number of outer reference points, the better the accuracy. The number of outer reference points is preferably four or more.

Next, as shown in FIG. 11A which is a schematic plan view, with respect to the final shape, each of the first inner point AF corresponding to the inner reference point A and the outer reference points B1 to B8 corresponding to the inner reference point A. First outer points BF1 to BF8 are set (step S20), and positions of cross-sectional lines D1 to D7 in the final shape connecting the first inner point AF and the first outer points BF1 to BF8 are set (step S30). ).

Next, in step S40, as shown in FIG. 11, division points B11 to B82 obtained by dividing the actual lengths of the respective sectional lines at the set ratio are set for the respective sectional lines D1 to D7. In this example, since two setting ratios are set, two dividing points B11 to B82 are set for each of the sectional lines D1 to D7. The accuracy increases as the setting ratio is increased. However, the calculation cost and time cost required for the design increase as the setting ratio increases. Preferably four or more.

Next, the sectional lines in the final shape passing through all the dividing points B11 to B82 corresponding to the set ratios are determined as first endless annular lines C1 and C2. At this time, for example, a line having the shortest distance between adjacent division points B11 to B82 is employed. Alternatively, the first endless annular lines C1 and C2 may be set as endless annular lines in which adjacent division points B11 to B82 are connected by a straight line without being a cross-sectional line. However, the accuracy is better when the cross-section line is adopted.

Next, in step S50, the first line length of the first endless annular line for each set ratio determined in step S40 is calculated. In this example, two first line lengths are obtained.

The first line length in the final shape is obtained by performing a final shape molding simulation using, for example, CAE. Further, for example, the final shape product may be manufactured by actually performing press molding and measured by an optical measurement method or the like.

Next, in step S60, as shown in FIG. 12, a straight line connecting the inner reference point A (corresponding to the second inner point) and the outer reference points B1 to B8 in the plate material 1 before forming is formed in a preformed shape. By setting the positions of the section lines D1 to D7 and dividing each of the above straight lines at the set ratio used in the final shape, division points B11 to B82 are set. Then, for each set ratio, the position of the endless annular line connecting the adjacent division points B11 to B82 with a straight line is specified as the position to be the second endless annular line in the preformed shape.

In step S70, the second line length for each set ratio is obtained from the first line length for each set ratio obtained in step S50. Specifically, the second line length is set for each set ratio from a range that is not less than 0.8 times and not more than 1.2 times the first line length.

Next, in step S80, the shape in which the length of the position that becomes the second endless annular line in the preformed shape set in step S60 becomes the second line length set in step S70 is a preformed shape. Set as.

When determining the length of the position that becomes the plurality of second endless annular lines, for example, the shape of the preformed shape is determined from the position including the location where the degree of curvature change is relatively large in the final shape. After the tentative determination, the length of the position of the other second endless annular line is corrected to determine the shape of the final preformed shape.

Here, the ratio of the second line length to the first line length is preferably not less than 0.6 times and not more than 1.4 times, and ranges from 0.8 times to 1.2 times as described above. It is more preferable that Most preferably, it is in the range of 0.9 to 1.1 times. When the ratio is less than 0.6 times, the line length is insufficient at the time of final molding, and there is a possibility that cracking may occur or the yield may be reduced. On the other hand, if the ratio exceeds 1.4 times, the wire length is excessive at the time of final molding, and wrinkles may occur on the product surface. On the other hand, it has been confirmed that the occurrence of cracks and the occurrence of wrinkles on the product surface can be greatly reduced by adjusting to a range of 0.8 times to 1.2 times. That is, the boundary value in the range of 0.8 times to 1.2 times is not a critical value. Since it was confirmed that a high yield was secured at least within this range, this value was specified.

In this case, the processed shapes after the processing in each of the temporary forming steps are the first endless annular lines C1 and C2 in the final shape and the second endless annular lines in the processed shape after the processing. It is preferable to set for each of the temporary forming steps so as to fall within the allowable range. However, it is only necessary that the preformed shape one stage before forming into the final shape satisfies the above conditions.

[Examples regarding the first embodiment]
Example 1
Example 1 below is an example in which cross-sectional portions for adjusting the cross-sectional line length are set in a lattice shape.

The final shape imitating an automobile wheel house part shown in FIG. 5 was created by a multi-stage press molding process.

As the plate material 1, mild steel having a plate thickness of 0.7 mm was used, and a rock beat was provided on the outer peripheral side of the product forming portion, and complete overmolding was performed to verify the effect of the present invention.

Fig. 6 (a) shows a preformed shape that is generally performed for comparison. A pre-formed shape for comparison (FIG. 6A) is a pre-formed shape obtained by projecting a ball head without using the method of the present invention. The pre-formed shape for this comparison is formed into a hemispherical shape.

FIG. 6 (b) shows a preformed shape obtained by the method of the present invention. This preformed shape has a shape in which the central portion is slightly depressed so as to satisfy the condition of the obtained sectional line length.

Here, in the setting of the pre-formed shape of the method of the present invention, the final shape was analyzed using the analysis model, and the pre-formed punch shape (pre-formed shape) was calculated from the result.

The mesh size of the analysis model was 5 mm, and the mold was a rigid body. Molding analysis was performed by a dynamic explicit method using LSDYNA ver 9.7.1R5. The cross section for obtaining the preformed shape was set in the above-mentioned coordinate system, as shown in FIG. The preformed shape design uses the above coordinate system in the design space of the preformed shape, and sets 120 cross sections, 60 cross sections each on the XZ plane and YZ plane, at the same coordinate position as the above 120 cross sections. At the position, the pre-formed shape was designed so that the ratio of the cross-sectional line length to the final shape was 0.8 or more and 1.2 or less. At this time, for comparison, the shape was calculated such that the overhang of the spherical head and the outline of the preformed shape according to the present invention in the top view coincide.

The experimental results are shown in Table 1.

As can be seen from Table 1, when manufacturing was carried out by a single molding without pre-molding, strain was concentrated on the die shoulder and cracking occurred. Further, when the pre-formed shape was designed without using the method of the present invention, the cross-section line length was not taken into account, so that large wrinkles occurred at the punch bottom and necking occurred at the punch shoulder. On the other hand, when the preformed shape was determined using the method of the present invention, it was confirmed that wrinkles, cracks, necking, etc. did not occur. Thus, by providing the method of the present invention, good results can be obtained.

(Example 2)
Example 2 is an example in which the location of the cross section for adjusting the cross sectional line length is set to be radial.

In the second embodiment, the internal set point P0 is set at the position of the centroid when the final shape is viewed from the direction along the press direction as shown in FIG. 7 with respect to the final shape using the analysis model. A plurality of lines are set radially from the internal set point P0. A broken line position is a position of a plurality of lines.

Next, based on the cross-section line lengths at a plurality of set line positions, the cross-section line length ratio with respect to the final shape of the preformed shape was calculated to be 0.8 or more and 1.2 or less at each cross-section position. The shape preformed based on the result is shown in FIG. The broken line position is the section line length position.

Here, the plate material and final shape other than the setting of the cross-sectional position were set in the same manner as in Example 1 above.

Also in this Example 2, it was confirmed that no wrinkles, cracks, necking, etc. occurred. Thus, it is possible to obtain a good result also by providing this invention method.

[Examples relating to the second embodiment]
The final shape imitating an automobile wheel house part shown in FIG. 13 was created by a multi-stage press molding process.

An inner reference point is set at the centroid position of the final shape, a plurality of points are arranged on the outer peripheral contour (outline) of the molding area of the final shape, and the inner reference point and the plurality of points are individually connected. Positions that divide the cross-section line into 10 parts were set as division points, and nine cross-section lines (first endless annular lines) were set according to the division positions (see FIG. 14).

Next, the preformed shape was designed so that the lengths of the nine cross-sectional line positions were 0.8 times or more and 1.2 times or less than the final shape. FIG. 15 shows an example of the preformed shape.

For comparison, the final shape was also processed by one molding without pre-molding.

The experimental results are shown in Table 2.

As can be seen from Table 2, when manufacturing was performed by one molding without pre-molding, strain was concentrated on the die shoulder and cracks occurred. Further, when the pre-formed shape was designed without using the method of the present invention, the cross-section line length was not taken into account, so that large wrinkles occurred at the punch bottom and necking occurred at the punch shoulder.

On the other hand, when the preformed shape was determined using the method of the present invention, it was confirmed that wrinkles, cracks, necking, etc. did not occur. Thus, by providing the method of the present invention, good results can be obtained.

1 Plate 1 (blank)
P0 Internal set point A Inner reference point AF Inner point B11-B82 Split point B1-B8 Outer reference point BF1-BF8 Outer point C1, C2 First endless annular line D1-D7 Cross section line

Claims

In a method for forming a plate material that is plastically deformed from its preformed shape to its final shape after plastic deformation is applied to the plate material,
For the cross-sections at a plurality of positions in the final shape, the ratio of the cross-sectional line length in the pre-shaped shape cut in the same surface to the cross-sectional line length in the final shape cut in one surface is an allowable value set in advance. A method for forming a plate material, wherein the pre-formed shape is determined so as to be within the range.
2. The plate material forming method according to claim 1, wherein the range of the preset allowable value is a range of 0.8 times to 1.2 times.
The position of the cross section of the plurality of places is set so as to be a lattice shape when viewed from the direction along the plate thickness direction in the plate material before forming, The plate material according to claim 1 or 2, Molding method.
Set an internal set point in the final shape molding area, set a plurality of lines passing through the internal set point and extending in different directions, and set the cross-sections at the plurality of positions at the set multiple lines The method for forming a plate material according to claim 1 or 2, wherein:
The method for molding a plate material according to claim 4, wherein the internal set point is set at a position of a centroid when the final shape is viewed from a direction along a plate thickness direction of the plate material before molding. .
The preformed shape is molded into the preformed shape through two or more temporary molding steps,
For each processed shape after processing in each of the temporary forming steps, the cross-sectional line length in the processed shape after the processing with respect to the cross-sectional line length in the final shape at the same cross-sectional position is the cross section of the plurality of locations, respectively. The plate material according to any one of claims 1 to 5, wherein each processed shape after the processing in each of the temporary forming steps is determined so as to be within a range of a preset allowable value. Molding method.
The method for molding a plate material according to any one of claims 1 to 6, wherein each molding is press molding.
After the plastic material is plastically deformed and formed into a pre-formed shape, the pre-formed shape is set when the plastic shape is deformed from the pre-formed shape to the final shape,
For the cross-sections at a plurality of locations in the final shape, the ratio of the cross-sectional line length in the pre-shaped shape to the cross-sectional line length in the final shape at the same cross-sectional position is within a predetermined tolerance range, respectively. A method for setting a preformed shape, wherein the preformed shape is determined.
The method for setting a preforming shape according to claim 8, wherein the positions of the cross-sections at the plurality of locations are set in a lattice shape.
The method for setting a preformed shape according to claim 8, wherein the positions of the cross-sections at the plurality of locations are set radially.
After plastically deforming the plate material and forming it into a preformed shape, when plastically deforming from the preformed shape to the final shape,
In addition to setting the inner reference point in the molding area of the final shape, set a plurality of outer reference points on the outer peripheral contour line of the molding area,
For the final shape, a plurality of cross-sectional lines individually connecting the first inner point corresponding to the inner reference point and the first outer points corresponding to the outer reference points are set, and the set cross-sectional lines Is determined at a preset ratio, each division point is obtained, and the length of an endless annular line obtained by connecting adjacent division points is a first line length,
In the pre-formed shape, at each dividing point obtained by dividing a plurality of cross-sectional lines connecting the second inner point corresponding to the inner reference point and each second outer point corresponding to each outer reference point at the set ratio, When the length of the endless annular line obtained by connecting adjacent dividing points is the second line length,
A method for forming a plate material, wherein the preforming shape is determined so that a ratio of the second line length to the first line length is within a preset allowable range.
12. The plate material forming method according to claim 11, wherein the range of the allowable value is in a range of 0.8 times to 1.2 times.
The plate material forming method according to claim 11 or 12, wherein the endless annular line is a cross-sectional line passing through a plurality of corresponding dividing points.
A plurality of the set ratios are set, and the preforming shape is determined so that the ratios of the second line length to the first line length at each set ratio are all within the allowable value range. The method for forming a plate material according to any one of claims 11 to 13.
The method for forming a plate material according to any one of claims 11 to 14, wherein the internal reference point is set at a centroid of a forming region of the final shape.
The preformed shape is molded into the preformed shape through two or more temporary molding steps,
For each processed shape after processing in each of the temporary forming steps, processing in each of the temporary forming steps so that the ratio of the second line length to the first line length is all within the allowable range. The method for forming a plate material according to any one of claims 11 to 15, wherein each subsequent processed shape is determined.
The method for forming a plate material according to any one of claims 11 to 16, wherein each forming is press forming.
In the molding of a plate material that is plastically deformed from the preformed shape to the final shape after plastic deformation is applied to the plate material, the above preformed shape setting method,
In addition to setting the inner reference point in the molding area of the final shape, set a plurality of outer reference points on the outer peripheral contour line of the molding area,
For the final shape, a plurality of cross-sectional lines individually connecting the first inner point corresponding to the inner reference point and the first outer points corresponding to the outer reference points are set, and the set cross-sectional lines Each division point to be divided at a preset setting ratio, the length of the endless annular line obtained by connecting adjacent division points as the first line length,
In the pre-formed shape, at each dividing point obtained by dividing a plurality of cross-sectional lines connecting the second inner point corresponding to the inner reference point and each second outer point corresponding to each outer reference point at the set ratio, When the length of the endless annular line obtained by connecting adjacent dividing points is the second line length,
A preforming shape setting method, wherein the preforming shape is determined so that a ratio of the second wire length to the first wire length is within a preset allowable range.